Known systems and methods for indicating when the motor oil that lubricates moving internal parts of an engine needs to be changed are commonly based on elapse of time and/or miles traveled after the immediately previous oil change. The lengths of time and/or of mileage may be based on data developed through prior studies of the effect of vehicle operation on motor oil lubricating quality.
U.S. Pat. No. 6,513,367 mentions other known systems and methods. One involves using a dielectric sensor to monitor the quality of motor oil. Another involves estimating oil quality by tracking vehicle operation after the most recent addition of fresh motor oil. That patent also identifies various factors that contribute to contamination of engine motor oil.
One of those factors is soot created by combustion of fuel in the engine. The patent describes a sophisticated algorithm for estimating the amount of soot added to the motor oil by each combustion event in each cylinder. Specifically, soot addition is estimated as a function of fuel flow, load, coolant temperature, and an injection timing factor. When the quality of the oil has deteriorated to some defined extent suggesting that the oil be changed, a signal to that effect is given.
Certain engines, diesel engines especially, may have one or more aftertreatment devices in their exhaust systems for removing undesired materials from engine exhaust so that those materials don't enter the atmosphere. Such devices may at times require regeneration. As used here, “regeneration” of an aftertreatment device applies to any aftertreatment device that on occasion requires a specific cylinder combustion event that creates additional soot, HC, and the like in order to maintain effectiveness of the aftertreatment device.
One such device is a diesel particulate filter (DPF) that traps certain particulates in the exhaust. A DPF requires regeneration from time to time in order to maintain particulate trapping efficiency. Regeneration as applied to a DPF involves the presence of conditions that will burn off trapped particulates whose unchecked accumulation would otherwise impair DPF effectiveness. While “regeneration” of a DPF often refers to the general process of burning off DPM from a DPF, two particular types of DPF regeneration are recognized by those familiar with DPF regeneration technology as presently being applied to motor vehicle engines.
“Passive regeneration” is generally understood to mean regeneration that can occur anytime that the engine is operating under conditions that burn off DPM without having been initiated by a specific regeneration strategy embodied by algorithms in an engine control system. “Active regeneration” is generally understood to mean regeneration that is initiated intentionally, either by the engine control system on its own initiative, or by the driver causing the engine control system to initiate a regeneration, with the goal of elevating temperature of exhaust gases entering the DPF to a range suitable for initiating and maintaining burning of trapped particulates.
Active regeneration may be initiated before a DPF becomes loaded with DPM to an extent where regeneration would be mandated by the engine control system on its own due to the amount of DPM loading.
The creation of conditions for initiating and continuing active regeneration, whether forced by the control system on its on or by driver action, generally involves elevating the temperature of exhaust gas entering the DPF to a suitably high temperature to initiate and continue burning of trapped particulates. Because a diesel engine typically runs relatively cool and lean, the post-injection of diesel fuel is one technique used as part of a regeneration strategy to elevate exhaust gas temperatures entering the DPF while still leaving excess oxygen for burning the trapped particulate matter. Post-injection may be used in conjunction with other procedures and/or devices, a diesel oxidation catalyst ahead of the DPF for example, for elevating exhaust gas temperature to the relatively high temperatures needed for active DPF regeneration.
The post-injection of fuel for DPF regeneration however inherently creates certain additional exhaust constituants, including an excess of unburned fuel, to be exhausted from each combustion chamber. Hence, active regeneration of a DPF, even if only occasional, creates an additional contamination component in the exhaust created within the engine combustion chambers. Particulate filters used to reduce particulate emissions from diesel engines require periods of time at sufficient temperature to regenerate or burn off the collect soot. If the vehicle/engine duty cycle doesn't provide for the required particulate filter inlet temperature to be attained periodically, an alternate means of sufficient increase in filter inlet temperature must be employed. One such means is to use additional in-cylinder fuel injection pulse(s) late in the expansion stroke to provide a source of unburned fuel to the exhaust gas. This unburned fuel is then oxidized in an oxidation catalyst, causing a temperature increase in the exhaust gas entering the particulate trap sufficient to initiate regeneration.
In some cases the use of post injection can result in fuel deposition on the cylinder wall, ultimately leading to fuel dilution of the lubricating oil. This dilution results in lower viscosity and other property changes of the lubricating oil, reducing its effectiveness.